[analyzer] Shitfing a constant value by its bit width is undefined.

Citation: C++11 [expr.shift]p1 (and the equivalent text in C11).

This fixes PR18073, but the right thing to do (as noted in the FIXME) is to
have a real checker for too-large shifts.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@199405 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/StaticAnalyzer/Core/BasicValueFactory.cpp b/lib/StaticAnalyzer/Core/BasicValueFactory.cpp
index a6c400f3704d2fba9e103953c74cb1bdb9345779..8f93cee6263374a23daaff4bb4d59e583c1cbaa6 100644 (file)
--- a/lib/StaticAnalyzer/Core/BasicValueFactory.cpp
+++ b/lib/StaticAnalyzer/Core/BasicValueFactory.cpp
@@ -177,7 +177,7 @@ BasicValueFactory::evalAPSInt(BinaryOperator::Opcode Op,
 
       uint64_t Amt = V2.getZExtValue();
 
-      if (Amt > V1.getBitWidth())
+      if (Amt >= V1.getBitWidth())
         return NULL;
 
       return &getValue( V1.operator<<( (unsigned) Amt ));
@@ -195,7 +195,7 @@ BasicValueFactory::evalAPSInt(BinaryOperator::Opcode Op,
 
       uint64_t Amt = V2.getZExtValue();
 
-      if (Amt > V1.getBitWidth())
+      if (Amt >= V1.getBitWidth())
         return NULL;
 
       return &getValue( V1.operator>>( (unsigned) Amt ));

diff --git a/test/Analysis/bitwise-ops.c b/test/Analysis/bitwise-ops.c
index bf282eca27d4eac035d5f1f4174da647bee5c9fc..01daf4229625390b5fcd95c479084397642b4562 100644 (file)
--- a/test/Analysis/bitwise-ops.c
+++ b/test/Analysis/bitwise-ops.c
@@ -1,4 +1,4 @@
-// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.ExprInspection -verify %s
+// RUN: %clang_cc1 -analyze -analyzer-checker=core,debug.ExprInspection -triple x86_64-apple-darwin13 -Wno-shift-count-overflow -verify %s
 
 void clang_analyzer_eval(int);
 #define CHECK(expr) if (!(expr)) return; clang_analyzer_eval(expr)
@@ -11,4 +11,22 @@ void testPersistentConstraints(int x, int y) {
   // False positives due to SValBuilder giving up on certain kinds of exprs.
   CHECK(1 - x); // expected-warning{{UNKNOWN}}
   CHECK(x & y); // expected-warning{{UNKNOWN}}
+}
+
+int testConstantShifts_PR18073(int which) {
+  // FIXME: We should have a checker that actually specifically checks bitwise
+  // shifts against the width of the LHS's /static/ type, rather than just
+  // having BasicValueFactory return "undefined" when dealing with two constant
+  // operands.
+  switch (which) {
+  case 1:
+    return 0ULL << 63; // no-warning
+  case 2:
+    return 0ULL << 64; // expected-warning{{The result of the '<<' expression is undefined}}
+  case 3:
+    return 0ULL << 65; // expected-warning{{The result of the '<<' expression is undefined}}
+
+  default:
+    return 0;
+  }
 }
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